TRANSFORMER EFFICIENCY

Now YOU get to explain WFT you really want to know.

.... Phil

On a sunny day (Wed, 8 Jan 2014 23:14:49 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :

The heat it generates, subtract that from the input :-) that gives oy the ouptut.

It is a cheap method, use your finger.

With great difficulty.

There are a lot of factors at play, some of which are dependent on characteristics of the materials involved that aren't always easy to pin down. Moreover, how you use the transformer in your circuit matters.

Finally, for some applications the efficiency doesn't matter nearly as much as other things; usually bandwidth or fidelity of reproduction.

Factors that I know of are:

The resistance of the windings, the resistivity of the core material, the thickness of the laminations (if any), the nonlinear magnetic properties of the core material, the overall shape of the core and windings

I'm sure there's more.

I suspect that even in this day and age of high-falutin' computerized finite-element analysis, you'll still find that in practice anyone who can build you a transformer and have it possess the correct efficiency by design is someone who has designed and tested dozens or hundreds of similar transformers and is leaning on a wealth of practical information, rather than analysis from "first principles".

Hi Tim, If you wanted to keep it simple isn't there some leakage inductance (or is leakage the wrong term) that you see modeled as being in parallel ( I think) with the primary, and given the leakage inductance and the winding resistance you could calculate some loss.

George (not a transformer guy) Herold

If you are really determined, you could try studying some of the heavy electrical engineering textbooks from the 1940s and 50s. They will give the sort of information you need, but mainly aimed at the design of massive power-distribution transformers where you really do have to calculate first and build later.

That will give you some idea of the factors at work and the ball-park figures you can expect, then you will have to scale everything to suit the size of transformer you are interested in.

WHAT "first principle"? From the theoretical definition? Answer is 100 percent.

Ignore the bushwah and look at losses: IR winding losses and induced magnetic core losses; that will get you close to measured losses.

It's a good thing you didn't ask anybody to explain hysteresis!

That was not in his "domain".